1. Field of the Invention
The invention relates to a vehicle seat with a built-in cushion airbag device.
2. Description of Related Art
In a vehicle seat described in Japanese Patent Application Publication No. 2008-162546 (JP 2008-162546 A), a cushion airbag is provided on a seat lower side of a seat portion (seat cushion), and this cushion airbag is divided into a front-side inflating portion and a rear-side inflating portion. When the vehicle is involved in a frontal collision, the front-side inflating portion and the rear-side inflating portion inflate, such that the buttocks and thighs of a seated occupant are pushed upward toward a seat upper side. As a result, the seated occupant is inhibited from slipping forward toward the seat front side under a lap belt (a so-called submarine phenomenon), such that the waist of the seated occupant remains restrained by the lap belt. Japanese Patent Application Publication No. 2007-168599 (JP 2007-168599 A), Japanese Patent Application Publication No. 2007-320389 (JP 2007-320389 A), Japanese Patent Application Publication No. 2008-195202 (JP 2008-195202 A), Japanese Patent Application Publication No. 2001-239872 (JP 2001-239872 A), Japanese Patent Application Publication No. 2012-016970 (JP 2012-016970 A), and Japanese Patent Application Publication No. 2002-079862 (JP 2002-079862 A) each describe a vehicle seat with a built-in cushion airbag device.
However, in the vehicle seat with a built-in cushion airbag device described above, the rear-side inflating portion inflates relatively large and pushes the buttocks of the seated occupant upward toward the seat upper side, so there is a tendency for a load placed on the neck of the seated occupant to increase. That is, when the buttocks of the seated occupant are pushed upward toward the seat upper side by the rear-side inflating portion, the upper body of the seated occupant tries to move toward the seat upper side, but the head of the seated occupant wants to stay in position due to inertial force. Therefore, the head of the seated occupant is displaced so as to fall toward the seat front side. As a result, the load placed on the neck of the seated occupant increases. Thus, the vehicle seat with a built-in cushion airbag device described above has room for improvement regarding this point.